A fast aperture lens always garners attention and the Sigma 30mm f/1.4 EX DC HSM Lens is no exception. Photographers wasted little time in making this lens one of their favorites. Adding a relatively low price point, fast HSM autofocusing, small size and good build quality to the fast aperture puts the 30 f/1.4 in its own class.
At 2.97" x 2.3" (75.5mm x 59mm)(DxL) and 15.2 oz (430g), the Sigma 30 f/1.4 is relatively small and in the medium-light weight class. The 62mm filter diameter is somewhat unusual (some of Sigma's non-EX zoom lenses share this size). Build quality is very nice. If you like Sigma's standard slightly-speckled matte finish, you will like how this lens (and its included hood) feels. Mounted on a 1.6x body, this is a very nice handling lens.
I mentioned "Mounted on a 1.6x body" - Sigma designates this lens as a "DC" or digital camera lens. By digital camera, Sigma means a 1.5x/1.6x FOVCF Digital SLR. If you are using or plan to use a full frame body in the not-too-distant future, you might want to look at the alternatives. Framing like a 48mm lens on a full-frame body, the Sigma 30mm f/1.4 EX DC HSM Lens is as close to a classic 50mm lens as 1.6x body users can get. This is the focal length that many people used exclusively for a decade or more.
Sigma's HSM (Hypersonic Motor) internal autofocus is very nice - reasonably fast and very quiet. The quietness makes it seem even faster. The front element does not rotate and FTM (Full Time Manual) focusing is available. The manual focusing ring is smooth but somewhat stiff. The stiffness is not all bad as your hand will likely be holding the lens by/near this ring - If it turned too easily, you might produce OOF (out of focus) shots. AI Servo performance including accuracy is good.
The Sigma 30mm f/1.4 EX DC HSM Lens is somewhat soft wide open and steadily improves to quite sharp at f/2.8. Corner sharpness trails center sharpness by a stop or two. Bokeh from the 8-blade aperture is nice. Colors are decent, contrast is good. CA (Chromatic Aberration), though not absent, is very well controlled. Flare is well-controlled.
Some barrel distortion is noticeable if straight lines are near the edges. Digital camera-only lenses often show more vignetting than their full-frame counterparts when they are mounted on a 1.6x body, but the Sigma 30 competes well with these lenses. Some vignetting is visible in the corners wide open.
With a minimum focusing distance of 15.7" (40cm), the Sigma 30mm f/1.4 EX DC HSM Lens has a low native maximum magnification of 1:10.4 or about .1x. You will want larger subjects for this lens - Like people, landscapes, automobiles and other much-larger-than-bug-sized subjects. With the wide f/1.4 aperture, indoor photos of people are one of the best purposes for this lens. Remember - A close focusing distance will yield a shallow field of view at f/1.4.
What are the alternatives? Well, the closest comparable lens Canon makes is the full-frame-DSLR-compatible Canon EF 28mm f/1.8 USM Lens. These two lenses are more similar than they are different. The Canon 28 is 2/3 stops slower, shows more CA and flares even more easily. The Canon is lighter and slightly less expensive. Image quality is very similar.
Canon's most-similar lens aperture-wise is the slightly longer focal length Canon EF 35mm f/1.4 L USM Lens. This is a much more expensive option, but the Canon 35 L is a sharper lens (especially in the corners as can be expected as it is a full-frame lens). It is also larger, more flare prone, and it focuses closer. The Canon shows CA more frequently in specular highlights while the Sigma has more distortion.
The same lenses (as above) pictured without their lens hoods ...
The Sigma 30mm f/1.4 EX DC HSM Lens is available in Canon (reviewed), Nikon, Sigma, Pentax and Minolta mounts. My standard disclaimer: You should be aware that there are potential issues with third party lenses. Since Sigma reverse engineers (vs. licenses) manufacturer AF routines, there is always the possibility that a new body might not support an older third party lens. There are examples of this happening in the past. Sometimes a lens can be rechipped to be made compatible, sometimes not. Additionally, there is the risk of a problem that results in the lens and body manufacturers pointing blame at each other. However, Sigma USA's 4-year warranty is far superior to Canon USA's standard 1 year warranty.
Sigma includes a nice padded case in the Sigma 30mm f/1.4 EX DC HSM Lens box. This is a nice lens with many happy owners.